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United States Patent |
5,556,460
|
Berke
,   et al.
|
September 17, 1996
|
Drying shrinkage cement admixture
Abstract
A cement admixture composed of a low molecular weight oxyalkylene compound
and a comb polymer having carboxylic acid groups and oxyalkylene units
therein.
Inventors:
|
Berke; Neal S. (Chelmsford, MA);
Dallaire; Michael P. (Dover, NH);
Gartner; Ellis M. (Silver Spring, MD);
Kerkar; Awdhoot V. (Columbia, MD);
Martin; Timothy J. (West Sussex, GB2)
|
Assignee:
|
W.R. Grace & Co.-Conn. (New York, NY)
|
Appl. No.:
|
529389 |
Filed:
|
September 18, 1995 |
Current U.S. Class: |
106/823; 106/724; 106/729; 106/730; 106/802; 106/804; 106/805; 524/5; 524/27; 524/35; 524/44; 524/47; 524/55; 524/56; 524/58; 524/377; 524/386; 524/387 |
Intern'l Class: |
C09D 007/12; C08L 071/02 |
Field of Search: |
106/724,729,730,802,804,805,823
524/5,27,35,44,47,55,56,58,777,396,387
|
References Cited
U.S. Patent Documents
3486916 | Dec., 1969 | Cordon | 106/802.
|
3583880 | Jun., 1971 | Moren | 427/314.
|
3709707 | Jan., 1973 | Rehmar | 106/842.
|
4141737 | Feb., 1979 | Moon | 106/12.
|
4302251 | Nov., 1981 | Udag awa | 106/708.
|
4547223 | Oct., 1985 | Go oto | 106/802.
|
4946904 | Aug., 1990 | Akimoto | 525/327.
|
4975121 | Dec., 1990 | Sakuta | 106/724.
|
5016711 | May., 1991 | Cowan | 166/250.
|
5020598 | Jun., 1991 | Cowan | 166/293.
|
5142036 | Aug., 1992 | Akimoto et al. | 106/823.
|
5174820 | Dec., 1992 | Sakuta | 106/724.
|
5181961 | Jan., 1993 | Umak i | 106/724.
|
5413634 | May., 1995 | Sh awl | 106/696.
|
Foreign Patent Documents |
88115639.2 | Mar., 1989 | EP.
| |
94306623.3 | Mar., 1995 | EP.
| |
4676310 | Jun., 1973 | JP.
| |
54-110903 | Aug., 1979 | JP.
| |
55-027819 | Feb., 1980 | JP.
| |
56-00786 | Jun., 1981 | JP.
| |
57-145054 | Sep., 1982 | JP.
| |
5860293 | Apr., 1983 | JP.
| |
57-129880 | Feb., 1984 | JP.
| |
59-128240 | Jul., 1984 | JP.
| |
59-128242 | Jul., 1984 | JP.
| |
59-128251 | Jul., 1984 | JP.
| |
59-131552 | Jul., 1984 | JP.
| |
59-137383 | Aug., 1984 | JP.
| |
1145357 | Jun., 1989 | JP.
| |
251461 | Feb., 1990 | JP.
| |
Other References
CA 124:125141, "Process and admixtures for rapidly altering" . . . , Franz
et al. Apr. 95.
|
Primary Examiner: Brunsman; David
Attorney, Agent or Firm: Troffkin; Howard J.
Claims
What is claimed:
1. A cement admixture capable of enhancing inhibition of drying shrinkage
comprising a mixture of:
A) at least one oxyalkylene glycol, oxyalkylene ether glycol or mixtures
thereof having a molecular weight of up to about 4000; and
B) a comb polymer of a molecular weight of from 2,000 to 100,000 having (i)
carboxylic acid anhydride, free carboxylic acid or its ammonium, alkali or
alkaline earth metal salt and (ii) C.sub.2 -C.sub.5 oxyalkylene units or
mixtures of said units, wherein said units (i) or (ii) being pendant from
the polymer backbone chain and said units (ii) provide the majority of the
molecular weight of said polymer
said component A and component B are in a weight ratio of 1:1 to 100:1.
2. The admixture of claim 1 wherein component A is at least one low
molecular weight oxyalkylene compound selected from:
i) oxyalkylene glycols represented by the formula HOAOH or HO(AO).sub.n H
wherein A represents a C.sub.2 -C.sub.10 alkylene group, O represents an
oxygen atom, and n represents an integer of from 1 to about 80;
ii) oxyalkylene adducts of monoalcohols represented by the formula
RO(AO).sub.m H wherein R represents a C.sub.1 -C.sub.7 alkyl or a C.sub.5
-C.sub.6 cycloaklyl group, A represents a C.sub.2 -C.sub.4 alkylene group,
O represents an oxygen atom and m represents an integer of from 1 to about
10;
iii) oxyalkylene adducts of polyols represented y the formula Q[(OA).sub.p
OR'].sub.x wherein Q represents a C.sub.3 -C.sub.12 aliphatic hydrocarbon
residual group of a polyhydroxyalkane, each R' independently represents a
C.sub.1 -C.sub.14 alkyl or cycloalkyl group or hydrogen atom provided at
least one R' of said adduct represents a C.sub.1 -C.sub.14 alkyl or
cycloalkyl group; A represents a C.sub.2 -C.sub.4 alkylene group; O
represents an oxygen atom; p represents an integer of from 0 to about 10;
and x represents an integer of from 3 to 5; and
iv) mixtures of said oxyalkylene compounds.
3. The admixture of claim 2 wherein said component A is at least one
oxyalkylene glycol represented by the formula HO(AO).sub.n H.
4. The admixture of claim 2 wherein the component A is at least one
oxyalkylene adduct of monoalcohols represented by the formula RO(AO).sub.m
H.
5. The admixture of claim 2 wherein the component A is at least one
oxyalkylene adduct of polyols represented by the formula Q[(OA).sub.p
OR'].sub.x.
6. The admixture of claim 2 wherein the component B is a comb polymer
composed of a polymer having free carboxylic acid groups or alkali or
alkaline earth metal salts thereof and having units represented by the
formula
##STR4##
wherein Q is an ethylenic group
##STR5##
with R"' being hydrogen or C.sub.1 -C.sub.3 alkyl; B represents a tying
group which covalently bonds the (AO).sub.n R' group to the hydrocarbon
polymer backbone chain, said tying group B may be selected from carboxylic
acid ester group (--COO--), carboxylic acid amide group (--C(O)NH--),
alkenyl ether (--C.sub.x H.sub.2x O--, where x is 1-10), ether oxygen
(--O--) or where vicinal pendant groups provide carboxylic acid imide
group [(--C(O)).sub.2 N]; A is a C.sub.2 -C.sub.10 alkylene group or
mixtures thereof, preferably a C.sub.2 -C.sub.4 alkylene group or mixtures
thereof; O represents oxygen atom; R represents a hydrogen atom or a
C.sub.1 -C.sub.10 hydrocarbon (alkyl, aryl alkaryl or the like) group; n
has a value of from about 25 to 100 and sufficient to have the AO groups
provide a majority of the molecular weight of the polymer.
7. The admixture of claim 6 wherein the component B is a comb polymer
composed of a maleic anhydride/alkenyl ether copolymer in about 1 to 1
maleic anhydride to ether molar ratio and said alkenyl ether is
represented by the formula
##STR6##
wherein Q represents --CH.sub.2 --CH--; B represents C.sub.x H.sub.2x O--
wherein x is 1 to 10; A is C.sub.2 -C.sub.4 alkylene; O is oxygenation;
and R is hydrogen or a C.sub.1 -C.sub.10 hydrocarbon group.
8. The admixture of claim 6 wherein the component B is a polyoxyalkylene
glycol having ethylenically unsaturated carboxylic acid units grafted
thereto.
9. The admixture of claim 1 wherein the component B is a comb polymer
composed of a polymer having free carboxylic acid groups or alkali or
alkaline earth metal salts thereof and having units represented by the
formula
##STR7##
wherein Q is an ethylenic group
##STR8##
with R"' being hydrogen or C.sub.1 -C.sub.3 alkyl; B represents a tying
group which covalently bonds the (AO).sub.n R' group to the hydrocarbon
polymer backbone chain, said tying group B may be selected from carboxylic
acid ester group (--COO--), carboxylic acid amide group (--C(O)NH--),
alkenyl ether (--C.sub.x H.sub.2x O--, where x is 1-10), ether oxygen
(--O--) or where vicinal pendant groups provide carboxylic acid imide
group [(--C(O)).sub.2 N]; A is a C.sub.2 -C.sub.10 alkylene group or
mixtures thereof, preferably a C.sub.2 -C.sub.4 alkylene group or mixtures
thereof; O represents oxygen atom; R represents a hydrogen atom or a
C.sub.1 -C.sub.10 hydrocarbon (alkyl, aryl alkaryl or the like) group; n
has a value of from about 25 to 100 and sufficient to have the AO groups
provide a majority of the molecular weight of the polymer.
10. The admixture of claim 9 wherein the component B is a comb polymer
composed of a maleic anhydride/alkenyl ether copolymer in about 1 to 1
maleic anhydride to ether molar ratio and said alkenyl ether is
represented by the formula
##STR9##
wherein Q represents --CH.sub.2 --CH--; B represents C.sub.x H.sub.2x O--
wherein x is 1 to 10; A is C.sub.2 -C.sub.4 alkylene; O is oxygenation;
and R is hydrogen or a C.sub.1 -C.sub.10 hydrocarbon group.
11. The admixture of claim 9 wherein the component B is a polyoxyalkylene
glycol having ethylenically unsaturated carboxylic acid units grafted
thereto.
Description
BACKGROUND OF THE INVENTION
The present invention is directed to a cement admixture composition capable
of causing the combined effects of enhanced inhibition of drying shrinkage
of cement compositions while providing desired compressive strength of the
fully set composition. The present invention further provides an improved
concrete composition structural product.
Specifically, the present invention is directed to a cement admixture
composed of a synergistic combination of at least one low molecular weight
oxyalkylene polyol or ether adducts of polyols with at least one high
molecular weight comb polymer having a plurality of polyoxyalkylene chains
and carboxylic acid groups, as fully described hereinbelow.
Hydraulic cement compositions, such as mortar (cement, small particulate,
e.g. sand, and water), or concrete (cement, small particulate, large
particulate, e.g. gravel, and water), have certain properties which
substantially effect their durability. These properties include shrinkage
which normally occurs during curing and drying of the cement composition.
In addition, mortars and, in particular, concrete composition are used for
structural applications where enhanced strength of the cured structural
member is highly desired.
The term "drying shrinkage" shall refer herein and in the appended claims
to mean drying shrinkage and/or curing shrinkage done via ambient
conditions or under sealed conditions.
Conventional hydraulic cement compositions display a decrease in volume
with setting and drying of the cast composition. Although the magnitude of
the volume decrease is normally small, it is of extreme importance. This
shrinkage results in cracks and other defects which lower the
serviceability and durability of the resultant structure. The cracks
provide a path for air, water and corrosive materials such as chloride and
sulfate, to penetrate into the concrete structure, promoting carbonation
of the cement and corrosion of the metal reinforcing bars contained
therein. Further, the cracks provide a means for water to seep into and
through the structure. Such water entry further deteriorates the structure
through freeze-thaw cycling pressures exerted on the cement structure over
its life. It is highly desired to provide a cement which exhibits high
strength and is not subject to deterioration effects due to shrinkage and
freeze-thaw cycling.
Various attempts have been made to avoid the cracking phenomenon caused by
drying shrinkage. These include providing joints in the cement structure
to concentrate the site of crack formation at the joint and, thereby,
minimize such formation at other portions of the structure. Such joints
are expensive to install; are not applicable to certain structures such as
vertical walls, pillars and the like; and merely concentrate the area of
cracking but do not alleviate it.
Other attempts include varying the composition of the cement, varying the
methods of manufacture of concrete mix and varying the ballast material
used in forming the resultant concrete structure. None of these attempts
have resulted in a satisfactory solution. For example, cements have been
formulated with expansive admixtures in attempts to counter the shrinkage
of the concrete. However, it is difficult to determine the proper amount
of expansive admixture required to counter the drying shrinkage which
develops. The use of such materials thereby give rise to unpredictable
results.
With respect to overcoming the drying shrinkage of cement compositions,
such as concrete compositions, the literature teaches that various
oxyalkylene adducts are suitable for this purpose. For example, U.S. Pat.
Nos. 3,663,251 and 4,547,223 suggest the use of compounds of the general
formula RO(AO).sub.n H in which R may be a C.sub.1-7 alkyl or C.sub.5-6
cycloaklyl radical, A may be C.sub.2-3 alkylene radicals and n is 1-10, as
shrinkage reducing additives for cement. Similarly, U.S. Pat. No.
5,147,820 suggests terminally alkyletherified or alkylesterified
oxyalkylene polymers as useful for shrinkage reduction. Still further,
Japanese Patent Application 58-60293 provides the suggestion that
shrinkage reduction of cement can be accomplished by the addition thereto
of compounds which are aliphatic, alicyclic or aromatic group terminated
oxyethylene and/or oxypropylene repeating chain compounds.
One of the main advantages of using cement compositions, such as mortar and
concrete, to form architectural structural members is their ability to be
cast into a desired form which is capable of exhibiting high compressive
strength. With this in mind, the artisan does not desire to utilize
admixtures or other ingredients which cause a decrease in such strength.
Alkylene glycols and glycerols have been used in combination with cement
compositions for particular purposes. For example, these materials have
been added to inhibit water crystal formation when casting in cold climate
conditions or to inhibit the rate of evaporation of water in cement
slurries used in high temperature well bore hole applications. Further,
these additives have been used to provide a layer above cast, unset cement
composition to inhibit evaporation of water at the surface portion of the
structure and thereby enhancing the hydration of the cement at that
portion of the formation.
The above compounds when made part of an unset composition additives cause
the resultant cured composition to exhibit lower compressive strength than
its untreated counterpart. When the cement composition is a mortar or, in
particular, a concrete which is used to provide architectural structural
members for buildings, parking garages, bridge decks and the like, it is
essential that the mortar or concrete member exhibit high compressive
strength. Therefore, shrinkage reducing additives which decrease the
strength of the cured product have not found favor even though they
inhibit cracking in the member as discussed above.
It is highly desired to provide a cement admixture which can further reduce
the drying shrinkage attainable by the sole use of a glycol or glycol
adduct shrinkage reducing agent.
Further, it is highly desired to provide a cement admixture which is
capable of inhibiting drying shrinkage of structural cement compositions
while enhancing the compressive strength of the resultant cured structure.
Still further, it is highly desired to provide a cement admixture which can
form a neat composition which is capable of inhibiting drying shrinkage of
structural cement compositions while enhancing the compressive strength of
the resultant cured structure.
SUMMARY OF THE INVENTION
The present invention is directed to a cement admixture, and a method of
forming an improved structural hydraulic cement formation, which causes
further inhibiting of drying shrinkage attainable by the shrinkage agent
used while also causing enhanced compressive strength to the treated
formation. The admixture comprises a synergistic mixture of a low
molecular weight oxyalkylene glycol or ether adducts thereof with a high
molecular weight comb polymer having polyoxyalkylene chains and carboxylic
acid units as part of the comb structure.
DETAILED DESCRIPTION
It has been unexpectedly found that when one combines a low molecular
weight oxyalkylene compound, as described below, with a high molecular
weight comb polymer having polyoxyalkylene chains, one attains a cement
admixture composition which further inhibits drying shrinkage while
imparting desired compressive strength to a treated cement composition
structure.
Further, the present admixture has been found to provide the high
inhibition of drying shrinkage and desired compressive strength for
structural formation without suppressing the air entrainment capabilities
of the treated composition.
The subject cement admixture requires the use of a low molecular weight
oxyalkylene compound which can be selected from (i) an alkylene or
oxyalkylene glycol or (ii) oxyalkylene ether adducts of alcohols, or
polyols.
The molecular weight of these compounds may be up to about 4000 preferably
up to about 2000. The glycol can be represented by the formula HOAOH or
HO(AO).sub.n H (Formula I) where A represents a C.sub.2 -C.sub.10 alkylene
group such as ethylene, propylene, butylene and the like and mixtures
thereof with ethylene and propylene being preferred; O represents an
oxygen atom and n is an integer from 1 to about 80. The AO groups in a
particular glycol molecule may all be the same or may be different.
Examples of such glycols include 1,5-pentanediol, diethylene glycol,
dipropylene glycol, tripropylene glycol, di(ethoxy)di(propoxy) glycol and
the like. Further such glycols may include polyalkylene glycols,
poly(oxyalkylene)glycol, having molecular weights up to about 1200,
preferably up to about 1000. The AO groups forming the chain of such
glycols may contain a single type of alkylene ether group or a mixture of
alkylene ether groups which may be in block or random arrangement.
The oxyalkylene compounds used in forming the present admixture can also be
oxyalkylene ether adducts of mono alcohols or polyols. The oxyalkylene
adduct of monoalcohols is represented by the formula RO(AO).sub.m H
(Formula IIA) wherein R is hydrocarbon group, such as a C.sub.1 -C.sub.7
alkyl or a C.sub.5 -C.sub.6 cycloalkyl, preferable a C.sub.3 -C.sub.5
alkyl group. Examples of such R groups are methyl, ethyl, propyl,
isopropyl, n-butyl, isobutyl, t-butyl, n-pentyl, isopentyl, cyclopentyl,
cyclohexyl and the like. The preferred R groups are C.sub.3 -C.sub.5 alkyl
such as n-propyl, isopropyl, n-butyl, t-butyl and the like. Where there
are more than one R group of a polyol of Formula IIA it is preferred that
the R groups are the same. A is a C.sub.2 -C.sub.4 (preferably C.sub.2
-C.sub.3) alkylene group, such as ethylene, propylene and the like and
mixtures thereof in the same chain, and m is an integer of from 1 to about
10.
The oxyalkylene adduct of polyols are represented by the formula
Q[(OA).sub.p -OR'].sub.x, (Formula II B), wherein Q represents a C.sub.3
-C.sub.12 aliphatic hydrocarbon residual group of a polyhydroxyalkane, R'
independently represents a hydrogen atom or a C.sub.1 -C.sub.14 alkyl or
cycloalkyl group with the proviso that at least one R' group represents a
C.sub.1 -C.sub.14 alkyl or cycloalkyl group, A represents a C.sub.2
-C.sub.4 alkylene group or mixtures thereof, O represents oxygen atom, p
represents an integer of from 0 to 10 and x represents an integer of 3 to
5.
Illustrative agents of Formula II B employed according to the present
invention are derived from C.sub.3 -C.sub.12 aliphatic triols, such as
glycerol, 1,2,4-butanetriol, 2,3,4-pentanetriol,
2-ethyl-2-(hydroxymethyl)-1, 3-butanetriol, 2,,4-pentanetriol,
2-ethyl-2-(hydroxymethyl)-1, 3-propanetriol (trimethylol propane),
1,1,1-tris(hydroxymethyl)ethane, 1,2,6-trihydroxyhexane,
1,2,3-heptanetriol, and the like, C.sub.4 -C.sub.12 aliphatic tetrols
(e.g. 2,3,4,5-hexanetetrol, sorbitan, erythritol, pentaerythritol),
C.sub.5 -C.sub.6 sugar alcohols (including those compounds corresponding
to the formula HOCH.sub.2 (CHOH).sub.n CH.sub.2 OH wherein n is 3 to 6
such as xylitol, sorbitol, arabitol, mannitol, and the like),
monosaccharides (e.g. erythrose, threose, ribose, arabinose, xylose,
lyxose, allose, altrose, glucose, mannose, gulose, idose, galactose,
fructose, galactose, and the like), disaccharides (e.g. sucrose, lactose,
maltose) and alkyl glycosides (e.g. methyl glycosides, ethyl glycosides,
propyl glycosides, and other glycoside molecules wherein the alkyl
glycoside is an acetal formed by interaction of a C.sub.1 -C.sub.20
alcohol with a carbonyl group of a mono- or a disaccharide such as
glucose). Also suitable for use as the polyol are polysaccharides such as
cellulose, hydroxycellulose, chitin, guar, and starches as well as
hydroxy-containing substances such as tetrahydrofuran oligomer, oxetane
oligomers, sorbitol oligomers, glycerol oligomers, and the like.
Where there are more than one alkyl group represented by R' above,
preferably the R's are the same alkyl group. Illustratively, R' is methyl,
ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, amyl, t-amyl, hexyl,
heptyl, octyl, 2,4,4-trimethylpentyl, nonyl, decyl and the like. R' is
preferably a C.sub.4 -C.sub.5 tertiary alkyl group.
The preferred polyol components have the formula
##STR1##
where R.sub.1, R.sub.2 and R.sub.3 are each hydrogen or a C.sub.1
-C.sub.14 alkyl group with the proviso that at least one of R'.sub.1,
R'.sub.2 or R'.sub.3 is a C.sub.1 -C.sub.14 alkyl group, A is a C.sub.2
-C.sub.4 alkylene group and x, y and z are each selected from an integer
from 0-10. Preferably R.sub.1 and R.sub.3 are the same alkyl group, such
as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, amyl, t
-amyl, hexyl, heptyl, octyl, nonyl, decyl and the like. Most preferably,
R.sub.1 and R.sub.3 are the same C.sub.4 -C.sub.5 tertiary alkyl group.
Mixtures can be employed including mixtures of additives with different
alkyl groups and/or different oxyalkylene groups; mixtures of 1,2 diether,
1,3 diether and 1,2,3 triether are preferred.
The preferred compounds of Formula II B' are those having R' representing a
butyl group, A representing an ethylene or propylene and each x and z is 2
or 3. The most preferred adduct is dipropylene glycol mono-t-butyl ether
and tripropylene glycol mono-t-butyl ether.
In the case of the derivatives of glycerin, preferred components of the
subject admixture are those having the following formula:
##STR2##
wherein R.sub.1 and R.sub.3 are C.sub.1 -C.sub.16 alkyl groups, preferably
t-butyl or t-amyl groups, R.sub.2 is hydrogen, x and z are each 4-10 and A
is propylene. The preparation of such materials is shown, for example, in
U.S. Pat. Nos. 2,932,670, 2,932,616 and 4,241,224.
The present invention further requires a high molecular weight comb polymer
wherein the pendant chains of the polymer have a plurality of oxyalkylene
or carboxylic acid groups and said oxyalkylene groups provide a major
component of the polymer.
The term comb polymer shall mean herein and in the appended claims
copolymers having (i) carboxylic acid anhydride, free carboxylic acid or
its ammonium, alkali or alkaline earth metal salt of carboxylic acid units
and (ii) C.sub.2 -C.sub.5 oxyalkylene units therein and wherein the
carboxylic acid units or oxyalkylene units are pendant to the polymer
backbone structure and wherein the oxyalkylene units provide a majority of
the molecular weight of the comb polymer.
The polymer may have units which can be generally represented by the
formula
##STR3##
wherein Q is a fragment of the polymer backbone chain such as a
hydrocarbon fragment of a residual of an ethylenic group which has a
pendant group represented by B(AO).sub.n R; B represents a tying group
which covalently bonds the (AO).sub.n R' group to the hydrocarbon polymer
backbone chain, said tying group B may be selected from carboxylic acid
ester group (--COO--), carboxylic acid amide group (--C(O)NH--), alkenyl
ether (--C.sub.x H.sub.2x O--, where x is 1-10) , ether oxygen (--O--) or
where vicinal pendant groups provide carboxylic acid imide group
[(--C(O)).sub.2 N]; A is a C.sub.2 -C.sub.10 alkylene group or mixtures
thereof, preferably a C.sub.2 -C.sub.4 alkylene group or mixtures thereof;
O represents oxygen atom; R represents a hydrogen atom or a C.sub.1
-C.sub.10 hydrocarbon (alkyl, aryl alkaryl or the like) group; n has a
value of from about 25 to 100 and sufficient to have the AO groups provide
a majority of the molecular weight of the polymer.
In addition to the polymer units represented by Formula III above, the
polymer hydrocarbon backbone chain may contain free carboxylic acid
anhydride, the free carboxylic acid or its salt pendant groups.
The polymer may be a homopolymer or a copolymer with other copolymerizable
units. The copolymerizable monomeric units may be randomly distributed in
the polymer structure or may be alternating with the above structure I.
Further, the copolymer may contain either one or more than one type of
structure III units within the polymer structure and the units may be
random or block configuration. Further, the AO chains of any polymer may
be made up of a single oxyalkylene group, such as oxyethylene,
oxypropylene or the like or mixtures of said groups and said mixture of AO
groups may be in block or random configuration.
The molecular weight of the comb polymers found useful in the subject
admixture composition have a weight average molecular weight of from about
2,000 to 100,000, preferably from about 2,000 to 50,000 and most
preferably from about 2,000 to 25,000. Further, at least about 50,
preferably at least 60 percent by weight of the polymers molecular weight
should be attributable to the molecular weight of the AO units therein.
Examples of polymers found useful in the present invention have been
disclosed in U.S. Pat. Nos. 4,946,904; 5,142,036; 5,362,323; 5,393,343;
4,471,100 and 5,369,198, the teachings of which are incorporated herein by
reference. U.S. Pat. Nos. 4,946,904 and 5,362,323 disclose maleic
anhydride/alkenyl ether comb polymers and their hydrolyzed product in
which the oxyalkylene groups are linked to the backbone polymer chain by
an alkenyl ether group. U.S. Pat. No. 5,142,036 discloses a maleic
anhydride/alkenyl ether copolymer which further has oxyalkylene groups
linked by maleic ester groups. U.S. Pat. No. 5,393,343 discloses
polyacrylic acid amide/imide polymers wherein the oxyalkylene chain is
linked to the backbone polymer chain by amide groups and vicinal
carboxylic acid units which form imide groups. This polymer may further
contain unreacted carboxylic acid groups or salts thereof. U.S. Pat. Nos.
4,471,100 and 5,369,198 disclose copolymers which link the oxyalkylene
group to the backbone polymer chain by carboxylic acid ester groups.
It is understood that when an oxyalkylene chain is pendant through a
carboxylic acid anhydride (e.g. maleic acid unit) or free carboxylic acid
(e.g. acrylic acid unit), all acid units may not be utilized in such
linkage and remain as acid units.
Alternately, the comb polymer of the present invention may be a copolymer
having a poly(oxyalkylene) backbone which have carboxylic acid containing
units grafted to the backbone polymer chain. The grafting is normally
accomplished by free-radical initiated grafting of ethylenically
unsaturated monomers having carboxylic acid groups therein. It is
believed, though not meant to be a limitation to the present invention
that the grafting occurs through a secondary carbon atom on the backbone
(one having only one carbon--hydrogen bond). The ethylenically unsaturated
carboxylic acid containing monomer may be, for example, acrylic acid,
methacrylic acid, itaconic acid and the like as well as their C.sub.1
-C.sub.3 alkyl esters. When the poly(oxyalkylene) polymer has hydroxy
termination groups, a small degree of esterification between the hydroxyl
and carbonyl group may also be present and additional carboxylic acid
units be pendant therefrom. Comb polymers of this type are described in
U.S. Pat. No. 4,814,014, the teaching of which is incorporated herein by
reference.
The polymers of the instant invention may differ from that disclosed in the
cited references or elsewhere as the polymers presently required must have
oxyalkylene units forming the major component (at least 50 wt. percent) by
weight of the polymer. Further the present polymer may contain other
copolymerizable units provided the above requirement is met. For example,
the copolymer may further have styrene, methyl vinyl ether, vinyl
pyrrolidone and the like units as part of the polymer structure.
Various materials have been used to enhance the fluidity of cement
compositions. Such materials are generally referred to as cement
plasticizers or superplasticizers for cement compositions and include, for
example, condensation products of naphthalenesulfonate-formaldehyde,
condensation products of melamine sulfonate formaldehyde, lignon,
polyacrylates as well as oxyalkylene derivatives described hereinabove.
However, it has been found that most common cement plasticizers and
superplasticizers, when added to low molecular weight oxyalkylene drying
shrinkage inhibitor agents do not cause a further enhancement of the
drying shrinkage activity of the shrinkage agent and, further, may not
overcome the suppression of compressive strength observed when cement
compositions are treated with such agents. It has been unexpectedly found
that the present combination provides the desired effect of enhancing the
inhibiting drying shrinkage over that attained by the subject low
molecular weight shrinkage reducing agent while providing desirable
compressive strength to cement compositions, in particular to
architectural structural concrete compositions.
The subject cement admixture composition should contain component A to
component B in a weight ratio of from about 1 to 100 and preferably from 3
to 20. The admixture may be neat or be composed of an aqueous solution of
the required combination. It has been unexpectedly found that the required
components A and B are substantially miscible in one another and can
provide a storage stable composition with very small amounts (e.g. 10
weight percent) water. Thus, the present composition does not require the
addition, transportation and storage of large amounts of water. Aqueous
solutions preferably contain the combination of components in from 10 to
50 weight percent although greater or lesser concentrations may be
suitable in certain instances.
The admixture composition of the present invention may be used with
hydraulic cements suitable for architectural structural application, such
as ordinary, quick-hardening and moderate-heat portland cements, high
alumina cements, blast-furnace slag cement and the like. Of these,
portland cements of the ordinary and quick-hardening types ae particularly
desired and most readily used to form architectural structural members.
The active components of the cement admixture of the present invention
should be present in from about 0.1 to about 3, preferably about 0.5 to
about 3 and most preferably from about 1 to about 2 weight percent based
on the weight of cement content of the cement composition being treated.
The quantity of water used for setting the cement composition can vary
within the weight ratios of water to cement of from about 0.2:1 to 0.6:1,
preferably 0.3:1 to 0.5:1. Aggregate, such as pebble, gravel, sand, pumice
or fired perlite, as required may be employed in conventional amounts.
The improved cement of the present invention is composed of a substantially
uniform mixture of a hydraulic cement and the subject cement admixture
composed of at least one component A with at least one component B which
are described above. The improved cement may be formed at any stage of the
cement's formation or use, such as by applying the admixture to cement
powder during the grinding or blending with other dry materials to prepare
a specific type of cement. Although small amounts of water may be present
during the blending, the amount of water will be insufficient to cause
substantial hydration of the cement.
Alternately, an improved cement composition can be formed in situ during
the course of preparing a cement composition such as a mortar mix or a
concrete. The components of the admixture composition can be added
together as a single composition or they can be added separately as
separate material or as part of the water of hydration. When the admixture
is in the form of an aqueous solution, the water content of the solution
should be calculated as part of the total water content of the cement
composition.
Various conventional ingredients may be optionally used. Among the
optionally employable ingredients are: conventional hardening
accelerators, e.g. metal chlorides such as calcium chloride and sodium
chloride, metal sulfates, such as sodium sulfate, and organic amines such
as triethanolamine; ordinary hardening retarders, e.g. alcohols, sugars,
starch and cellulose; reinforcing-steel corrosion inhibitors such as a
sodium nitrate and calcium nitrite; water-reducing agents, amines and
their derivatives, alkanolamines, and inorganic salts such as borates,
phosphates, chlorides and nitrates; and the like. The quantity of such an
optional ingredient or ingredients is usually 0.05-6% by weight of the
cement.
The addition of the cement admixture composition of the present invention
to a cement will markedly reduce the drying shrinkage of the resulting
cement composition (e.g. mortar and concrete) above that achievable by the
use of the low molecular weight compound and will exhibit desired
compressive strength compared with that of untreated composition or
relative to cement composition having only one of the components of the
present admixture.
The following examples are given for illustrative purposes only and are not
meant to be a limitation on the invention, as defined by the claims
appended hereto. All parts and percentages are by weight unless otherwise
indicated. The term "S/S" indicates solid additive based on solid weight
of cement in the treated composition.
EXAMPLE 1
A series of micro concrete samples were made according to the following
procedure: 1800 parts of Type I Portland cement from three different
suppliers (Labeled "A", "B" and "C") were each blended with a mixture of
the following ASTM graded sands: 1069 parts of F-95 sand, 972 parts of
C-109, 972 parts of C-185, and 1847 parts of 15-S sand. The dry blending
was done in a Hobart mixer for approximately 0.5 minutes. The aggregate to
cement ratio was 2.7. To each of the blends was added 900 parts of
deionized water (w/c=0.5 for blank). The blends were thoroughly mixed in
the Hobart mixer for approximately nine (9) additional minutes to form the
micro-concrete reference materials.
The air content of the resulting micro concretes were measured using-ASTM
C-185 test method. The slump of each of the concretes was measured using
the ASTM C-143 test method. The micro concretes were then poured into
stainless steel prism molds (1".times.1".times.12") following ASTM C-490
test procedure. The mixes were cured for 24 hours at 100% RH and
20.degree. C. The prisms were demolded and stored in environmental chamber
maintained at 50% RH and 20.degree. C. The length of the prisms was
measured periodically using a length comparator following the ASTM test
procedure. Table 1 summarizes the data of % shrinkage reduction observed
in presence of MPD and MPD in combination with copolymer M-1511 in
comparison to the blank. The data indicate that combination of MPD with
copolymer M-1511 does not compromise the shrinkage reduction inhibition
performance of MPD.
TABLE 1
__________________________________________________________________________
Cement Dosage Dosage
W/C Slump
Air
Set-Time
Strength Shrinkage
Type DIOL
(%) Copolymer
(%) Ratio
(cm)
(%)
(min)
(% 1 Day)
(% 7 Day)
(% 28
Reduction
__________________________________________________________________________
B None
-- None -- 0.50
8.4 3.2
245 100 100 100 0%
None
-- M-1511
0.10
0.42
8.5 8.2
298 150 115 103 3%
MPD 1.0 None -- 0.48
8.1 5.3
295 78 98 97 17%
MPD 1.0 M-1511
0.10
0.41
9.6 8.3
346 130 139 113 27%
MPD 2.0 None -- 0.47
8.6 5.8
297 64 89 82 32%
MPD 2.0 M-1511
0.10
0.40
9.6 7.3
-- 85 117 101 45%
__________________________________________________________________________
EXAMPLE 2
Concrete samples were formed using a mix design proportioned by a
volumetric method according to ACI guidelines. The design requirements
were based on 517 parts Type I Portland cement, 1140 parts West Sand fine
sand, 740 parts Wrentham 0.75 inch coarse aggregate, 370 parts 1 inch Au
Claire gravel, 370 parts 0.625 inch Au Claire gravel and 370 parts 0.375
inch and 263 parts water. The fine aggregate was adjusted to project
design parameters of 5.5% air content, 0.51 water to cement ratio and a
slump of about 3.5 inches.
The concrete was formed according to ASTM C-192 specifications. The water,
coarse aggregate, fine aggregate and the appropriate admixture were
initially charged into a concrete mixer and mixed for one minute. The
Portland cement was then added and mixing continued for an additional
three minutes followed by a three minute rest period and a final two
minutes of mixing. The resultant samples were tested according to ASTM
C-143 for slump, ASTM C-138 for weight and yield, ASTM C-231 for air
content of the freshly mixed samples, ASTM C-192 for compressive strength
and ASTM C-157 for length change.
Mixtures were designed for constant workability modifying the amount of
water and sand.
The results of the tests are shown in Table 2. Sample 1 is a reference
untreated sample. Sample 2 contained only low molecular weight t-butyl
dipropylene glycol and dipropylene glycol in 2:1 ratio. Sample 3 contained
the same additives as Sample 2 with a polyoxyethylene-oxypropylene glycol,
(MW=5000) grafted with acrylic acid side chains of about 2 units. Sample 4
contained the same additives as Sample 2 with a polyacrylic acid having
oxyethylene ester and amide side chains on about 70 percent of the acrylic
acid and further having a small amount of tall oil fatty acid as air
entrainer.
TABLE 2
______________________________________
Compressive
%
Strength Shrinkage
Sam- Slump Air PSI Reduction
ple Admixture (in.) (%) 28 days (56 days)*
______________________________________
1 -- 3.75 5.3 5755 --
2 DPGBE (1) 3.25 5.6 5940 32%
PPG (0.5)
3 DPGBE (0.88)
3.5 5.7 6600 55%
PPG (0.44)
EoPoly (0.18)
4 DPGBE (1.25)
3.5 5.6 6540 63%
PAA/AO (0.17)
______________________________________
EXAMPLE 3
Concrete was formed in the same manner as Example 2 except that the design
was 658 parts Type I cement, 1750 parts 0.75 in coarse aggregate, 1230
parts West sand and 263 parts water. The design was for 6% air, water to
cement ratio of 0.40, and slump of 6-7 inch obtained by use of naphthalene
sulfonate superplasticizer.
The results are shown in Table 3.
TABLE 3
______________________________________
%
Plas-
Compressive
Shrink-
tic Strength age
Sam- Air PSI Reduc-
ple Admixture Slump W/C (%) 28 days tion
______________________________________
1 -- 6.75 0.40 5.5 5755 --
2 DPGBE 4.75 0.38 5.0 6540 95%
(1.2)
DPG (0.3)
P(EO)AA
(0.2)
______________________________________
P(EO)AA = polyoxyethylene oxypropylene glycol grafted with acrylic acid
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